What Virtual Machine are you using?
I have used Oracle Virtual Box and they have a pre-configured option when creating the Virtual Machine for Gentoo and Gentoo 64 bit?
Are you sure the Virtual Machine architecture matches the one of the *.iso you downloaded?

I have set everything as it should be (the arch i`m using is x86 so in VIRTUALBOX i have set one processor unit). I`m using older laptop, therefore i suppose i don`t have virtualization support.

I have also tried to install Gentoo using LiveDvd. I did whole instalation, but eventually I got same error message. It started to boot but it halted with the same message. So i don`t know whether i have bug in Virtualbox or what`s wrong.

There's a couple of threads on this subject hanging around the forums. It basically boils down to a weird interaction between something being done by the newer gentoo install disks and virtualbox running on a CPU that lacks VT-x or AMD-V.

As they are organised by date I'm not sure which ones have the 3.8 kernel

You can make a better guess knowing that 3.9 was introduced on 2013-04-29 and that it never got stable in Gentoo, we stabilized 3.10.7 instead on Wed Aug 21 12:11:35 2013 UTC. So, I think you would want to look for something in the first quarter or so of 2013.

As they are organised by date I'm not sure which ones have the 3.8 kernel

You can make a better guess knowing that 3.9 was introduced on 2013-04-29 and that it never got stable in Gentoo, we stabilized 3.10.7 instead on Wed Aug 21 12:11:35 2013 UTC. So, I think you would want to look for something in the first quarter or so of 2013.

Thank you, I'll go grab it now

This may seem a stupid question but, is this ok to load and install in VB?